Challenges In Sodium Cooled Fast Reactor Thermal Hydraulics

Abstract

Heat Transfer and Fluid flow phenomena (referred as Thermal Hydraulics) play a significant role in the safe and economical design of fast breeder reactors (FBR). The sodium cooled fast reactors have a very complex flow and temperature profile within the pool or the test vessel. The high temperature operating conditions (~540 deg.C) also impose stringent requirements on the thermal design of the components. The basic approach of thermal hydraulic design is to
minimize the conservatism involved without compromising on efficiency and safety in an economical manner. The fast reactor programme in India was launched with the commissioning of the 40 MWt Fast Breeder Test Reactor (FBTR). Even though the design of FBTR was similar to the French reactor RAPSODIE, thermal hydraulic analysis of the plant behaviour helped in gaining confidence in the operation of the reactor. Many transient tests including the
natural convection heat removal were conducted in FBTR which have validated our prediction. The design of the 500 MWe Prototype Fast Breeder Reactor (PFBR) with the pool type concept and the magnitude of scale up from FBTR necessitated important thermal hydraulic analysis to be conducted to firm up the design of the reactor. Computational capabilities and experimental facilities were established to understand and study the phenomena and to maximize the efficiency of thermal design of the reactor. With the construction of PFBR at an advanced phase and the commencement of the design for the future FBR’s an assessment of the existing capabilities and the challenges that are yet to overcome would provide a strategy for future thermal hydraulic analysis. This paper details the major thermal hydraulic activities carried out for PFBR, and the refinements required to be attempted in each of these areas to improve upon our thermal hydraulic prediction capabilities.